, 
426 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
The carcinecium is very rarely a naked gastropod shell; in most of 
the specimens seen it is either built up by a colony of Epizoanthus Amer- 
icanus, like the carcineecium of Eupagurus Kréyeri, from the same sta- 
tions, or is made up in a somewhat similar way by the single polyp of a 
species of Adamsia, the base secréted by the Adamsia being expanded 
on either side and united below so as to inclose the erab in a broadly 
conical cavity, with only a slight spiral curvature. The nuclei about 
which these polypean carcinecia are formed are of various origins; the 
majority of the Adamsia carcincecia appear to have been built upon 
fragments of pteropod shells, in some cases upon bits of worm-tubes, in 
one case upon the entire shell of a Cadulus, the greater part of the shell 
being left protruding from the base of the polyp. In the carcinecia 
formed by Epizoanthus the nucleus seems usually to have been absorbed, 
so that nothing is left distinguishable from the colony of polyps itself. 
In some case~ the Adamsia has completely overgrown a small EHpizoan- 
thus varcincecium, so that when the Adamsia is removed a perfect Hpi- 
zoanthus carcincecium is found beneath as a nucleus. The carcincecium 
of this species, and of H. gracilis as well, does not cover the animal to 
the same extent as is usual in the species of Lupagurus, the anterior 
part of the carapax evidently being constantly exposed, its induration 
fitting the animal for such exposure. The Hpizoanthus carcincecia are, 
however, very often disproportionally large for the crabs inhabiting 
them, having grown out either side until they are several times broader 
than long. In spite of these often enormous carcinecia, both species of 
the genus probably swim about by means of the ciliated dactyli of the 
ambulatory legs, as Spiropagurus spiriger has been observed to do by 
Stimpson (Proc. Acad. Nat. Sci. Philadelphia, 1858, p. 248 (86), 1859). 
Stations 865, 870, 871, 872, 873, 874, 876, 877, 878, 880; 65 to 252 fath- 
oms.” At many of these stations it occurred in very great abundance. 
Hemipagurus gracilis, sp. nov. 
This is a smaller and more slender species than the last, and is readily 
distinguished from it by the smooth carapax, the longer and more slender 
eye-staliks, the long and acicular ophthalmic scales, and by the narrow 
dactyli of the ambulatory legs being longer than the correspouding 
propodi. 
Male.—The carapax in front of the cervical suture is flat, smooth, 
nearly naked, and scarcely at all areolated. The anterior margin is rather 
more strongly sinuous than in Z. socialis, and the lateral lobes are 
slightly angular and each is tipped with a minute spine, as in that spe- 
cies, but the marginal carina between these spines is much less distinct. 
The eye-stalks are more than half as long as the carapax in front of 
the cervical suture, flattened and expanded distaliy, but only about half 
as broad as long. The eyes themselves are as in H. socialis. The oph- 
thalmie scales are more than half.as long as the eye-stalks, and are 
acicular and regularly acute. 
The ultimate segment of the peduncle of the antennula is as long as 
